Electrolysis of sulfate of cadmium solutions.



E. I. HUNT (Q W. T. GIDDEN.

ELECTROLYSIS OF SULFATE 0F CADMIUM SOLUTIONS.

APPLICATION FILED JUNE 24,1916.

Patented Apr. 30, 1918.

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EDWIN JAMES HUNT, 0F OLIDBURY, AND WILLIAM THOMAS GIDDEN, 0F WARLEY, I ENGLA'ND, ASSIGNORS TOCHANCE AND HUNT, LIMITED, 01? OLDBUIRY, ENGLAND.

ELECTROLYSIS 01E SULFATE 0F CADMIUIVI SOLUTIONS.

Specification of Letters Patent.

Patented Apr. 3t), will.

Application filed June 24:, 1916. Serial No. 105,587.

To all whom it may concern:

Be it known that we, EDWIN JAMES HUNT and WILLIAM THOMAS Gmnen, subjects of the King of Great Britain, residing, respectively, at Chemical Works, Oldbury, England, and Abbey Road, Warley, VVorcestershire, England, have invented new and useful Improvcments'inthe Electrolysis of S111- fate of Cadmium Solutions, of which the following is a specification. I

According to this invention in the electrolysis of'a sulfate of cadmium solution cont-aining free sulfuric acid with lead anodes free particles of undissolved lead compounds are prevented from contaminating the metal depositing at the cathode by preventing their access to the cathode and for this purpose a porous diaphragm may be interposed between the electrodes or the anodesor the cathodes may be surrounded with porous material.

The function of the diaphragm or porous material which may conveniently consist of asbestos cloth is to prevent insoluble lead compounds formed at the anodes from reaching the-cathodes but the diaphragm should be sufficiently porous to permit of as free circulation as possible of the liquor so that the electrolyte is substantially the same at the anode and cathode.

In working if it be found that at any moment the diaphragm is materially hindering the presence of free sulfuric acid at the cathode free acid may be added and this may be derived from the anode sections of the cell after separation of the suspended lead compounds;

In any case acid liquor may be continuously or intermittently withdrawn from either the anode sections, the cathode sections, or both.

By our invention a new result is obtained, viz., in the electrolysis with lead anodes of an acid solution of sulfate of cadmium present at both anode and cathode, a deposit of metal containing at most mere traces of lead in spite of the use of high density currents.

The cadmium sulfate solution to be electrolyzed may also contain sulfate of zinc and may contain about 10% of free sulfuric acid. Electrolysis is continued till the greater part of the cadmium has been deposited, without simultaneous deposition of any Lll'lC. The

spent electrolyte can then be neutralized with cadmium or zinc oxid or carbonate (or metal) and then treated with metallic zinc to precipitate the remaining cadmium. The resultin solution of sulfate of zinc can be dealt with as desired, while the precipitated cadmium with any excess of metallic zinc present can be dissolved in sulfuric acid and the solution, purified if necessary, treated as described for electrolytic recovery of the cadmium.

The anode mud produced in the rocess may be employed to assist in the puri cation of solutions of the sulfate of cadmium.

The neutral solution of sulfate of cadmium is treated to free it from iron in solution. For this purpose the preferably heated solution is agitated with a quantity of the lead peroxid (dependent on the quantity of ferrous iron present) formed by oxidation of the lead anodes during electrolysis, and obtained by separation from liquor in the anode compartment. To complete the separation of iron impurity, oxid or carbonate of cadmium or zinc may be added.

Or the sulfate liquor may be purified by treatment with manganese dioxid in slightly acid solution till oxidation of iron present is complete, with subsequent neutralization by addition of cadmium or ZlIlC oxid or car bonate, in which case the manganese passes into solution in amount equivalent to the iron separated.

In this case manganese dioxid may itself be derived from the anode mud since manganese in the electrolyte is separated at the anode as manganese dioxid. Thus the anode mud may be used as reagent for the removal of iron under either of the above conditions according as its content of lead peroxid or of manganese dioxid is the more useful.

The accompanying drawings which are more or less diagrammatic, show a cell embodying our improvements. In said drawings Figure 1 shows an elevation of the cell, and Fig. 2 a top plan thereof.

In the annexed drawings, 1 is the cell, 2

are lead anodes, 3 cathodes of sheet cadmium or other suitable metal, 4- are the porous diaphragnis of asbestos cloth adapted to permit free circulation of the liquor, 5 1s a supply pipe at the top of the cell for the supply portion of its cadmium content without deof electrolyte, and 6 are run off taps at the positing any considerable portion of its zinc 10 bottom of the cell. content, thereafter neutralizing the solution, What we claim is 2-, and adding metallic zinc in excess whereby 5 The herein described rocess of treating the remaining cadmium is precipitated, and

an acid solution containmg both sulfate of a zinc sulfate solution left. cadmium and sulfate of zinc which com- EDWIN JAMES HUNT.

prises electrolytically depositing themajor WILLIAM THOMAS GIDDEN. 

